Which screening tests for whether a compound affects cell viability?

• A. Genotoxicity
• B. Immunotoxicity
• C. Reproductive toxicity
• D. Cytotoxicity

Answer: (D)

Cell viability is about whether cells stay alive and functional. Screening for viability focuses on whether a compound kills cells or reduces their metabolic activity, i.e., lowers viability. Cytotoxicity specifically measures this kind of effect, so it is the test category that directly answers whether a compound is toxic to cells. In practice, cytotoxicity assays look at things like metabolic activity (MTT/MTS/resazurin-based tests), ATP content, or membrane integrity (LDH release) to gauge cell survival. By contrast, genotoxicity assesses DNA damage, immunotoxicity looks at immune system effects, and reproductive toxicity examines effects on fertility and development, none of which are direct measures of cell viability.